Dry cleaning is a process of major importance within the textile industry, specifically for the removal of hydrophobic stains which are difficult to remove by traditional aqueous washing methods. However, most commercial dry cleaning systems currently employ toxic and potentially environmentally harmful halocarbon solvents, such as perchloroethylene. The use of these solvents, and the need for their storage, treatment, and/or disposal creates major effluent problems for the industry, and this inevitably increases costs.
More recently, the use of carbon dioxide as an alternative to such systems has been reported. Thus, systems which employ liquid carbon dioxide in combination with surfactants containing a CO2-philic functional moiety have been proposed, whilst the use of more conventional surfactants in combination with supercritical carbon dioxide has also been disclosed. However, a major problem with carbon dioxide is its lower solvent power relative to other solvents. Furthermore, some of the procedures rely on the use of high pressure systems, and this is a clear disadvantage, since it presents an inherent safety risk, thereby lessening the attractiveness of the procedures.
In the light of the difficulties and disadvantages associated with traditional dry cleaning processes, the present inventors have attempted to devise a new and inventive approach to the problem, which allows the deficiencies demonstrated by the methods of the prior art to be overcome. Thus, the present invention seeks to provide a process for the dry cleaning of substrates, particularly for the dry cleaning of textile fibres, which eliminates the requirement for the use of either potentially harmful solvents or carbon dioxide in either the liquid or supercritical state, but which is still capable of providing an efficient means of cleaning and stain removal, whilst also yielding economic and environmental benefits.
The dry cleaning process, whilst being dependent on the use of solvents, does also incorporate aqueous media within the cleaning process, since fabrics and garments which are subjected to dry cleaning will inevitably contain significant amounts of water, which generally becomes entrapped therein by absorption or adsorption from the atmosphere. On occasions, further wetting of the fabrics or garments prior to dry cleaning may be desirable. However, the cleaning formulation used in conventional dry cleaning processes does not include added quantities of aqueous media therein and, in this way, dry cleaning differs from standard washing procedures. In the present invention, the cleaning process employs a cleaning formulation which is essentially free of organic solvents and requires the use of only limited amounts of water, thereby offering significant environmental benefits.